1. Field of the Invention
The present invention relates to a method for predicting remaining capacity of a battery, and more specifically, to a method for utilizing a voltage revision method and a current integration method in a software manner to predict remaining capacity of a battery more precisely.
2. Description of the Prior Art
In modern society, batteries are utilized to supply electronic products with power to avoid an inconvenience of using power lines. However, power of a battery is depleted with operation of the electronic product. Thus, charging is necessary for a battery. In general, portable electronic devices, such as mobile phones, utilize chargeable batteries as a power supply. For a user, it is important to know remaining capacity of a battery while operating an electronic device. As for the electronic device, it is also necessary to predict the remaining capacity of the battery, so as to preserve partial power for emergency use, such as a one-minute emergency call. However, under-prediction of the remaining capacity of the battery may result in a greater number of times that the battery is charged. This will shorten the battery's life. On the contrary, over-prediction of the remaining capacity of the battery could reduce power for emergency use or cause the user to encounter a shortage of power. Therefore, how to predict remaining capacity of a battery precisely should be a concern.
Related methods for predicting remaining capacity of a battery according to the prior art are provided as follows.
Intelligent battery technique (current integration method): This method involves putting a battery management chip inside a battery, such as a fuel gauge. The battery management chip can monitor a current status of the battery at any time so as to calculate the remaining capacity of the battery. Then, built-in software can directly read information stored in the battery management chip. The advantages of the method are low software loading and precise calculation of the remaining capacity. But, the method results not only in an increase of cost, but also additional power consumption caused by the power management chip (even in a turned-off state). In addition, after installing a new battery, a learning time is required to increase the accuracy of the remaining capacity calculation. And, a user's operation habits can also affect the accuracy (if the user often charges the battery before the power of the battery runs out, there will be a considerable error in the remaining capacity calculation). And, it is likely that a hardware cost of the battery management chip affects the selling price. Furthermore, it is difficult for this method to achieve the same accuracy in the remaining capacity calculation if the battery management chip is replaced with software.
Battery internal resistance method: This method involves establishing a battery remaining capacity-battery internal resistance table. Subsequently, remaining capacity of the battery can be calculated by a look-up method based on the said table after the mobile phone reads an internal resistance of the battery every period of time. However, a battery installed inside a mobile phone is usually a lithium battery. There is a considerable error in the remaining capacity calculation according to this method, since the internal resistance variation corresponding to the remaining capacity in a lithium battery is very small.
Voltage method: This method involves establishing a battery remaining capacity-battery voltage table in advance. Remaining capacity of a battery can be calculated by a look-up method based on the said table after the mobile phone reads a voltage of the battery every period of time. Simple calculation is the advantage of this method. But the drawback of this method is that the voltage of the battery affects the accuracy of this method, since the voltage of the battery varies with the power consumption of the battery. In addition, the accuracy of the battery remaining capacity-battery voltage table also affects the remaining capacity prediction greatly.
Method for adjusting voltage based on current: This method involves reading a current and a voltage of a battery at the same time, adjusting the voltage based on the current, and then determining remaining capacity of the battery based on a look-up method. The accuracy of this method is higher than the said voltage method. But the drawback of this method is increase of cost due to additional hardware for reading the current of the battery.
Method for adjusting voltage based on status: This method involves determining a current of a battery based on software rather than reading the current of the battery directly. Higher accuracy than the said voltage method and no additional cost are the advantages of this method. However, software cannot determine the actual current of the battery precisely. In addition, components installed inside the mobile phone, whose power consumption is directly proportional to time, can also increase calculation error.
In summary, all of the aforementioned methods for predicting remaining capacity of a battery have their respective drawbacks. Therefore, how to predict remaining capacity of a battery precisely without adding additional hardware should be a concern.